Contour following end effectors for lapping/polishing

ABSTRACT

End effectors are provided for performing surface lapping using a robot. The end effectors allow orthogonal surface contact in order to maintain optimum pressure applied by the robot. The end effectors include a base, a plate having a planar surface, a lapping pad that attaches to the planar surface of the plate, and a pivot-joint. The pivot-joint allows the plate to pivot about two axes. The base is attached to an arm of the robot. The two axes are substantially parallel to the planar surface.

GOVERNMENT LICENSE RIGHTS

[0001] This invention was made with Government support under U.S. Government contract F33615-97-2-3400 awarded by United States Air Force. The Government has certain rights in this invention.

RELATED APPLICATIONS

[0002] This patent application is related to concurrently-filed patent applications entitled “Spring-Loaded Contour Following End Effectors for Lapping/Polishing”, bearing attorney docket number BOEI-1-1102, and “Automated Lapping System”, bearing attorney docket number BOEI-1-1121, which are hereby incorporated by reference.

FIELD OF THE INVENTION

[0003] This invention relates generally to lapping and polishing surfaces and, more specifically, to robotic lapping and polishing.

BACKGROUND OF THE INVENTION

[0004] Injection-molded aircraft canopies and windshields offer tremendous benefits to aircraft in cost, weight, and impact tolerance. A major cost in this manufacturing process is the injection mold itself. Surfaces of canopies and windshields are finished to a quality similar to an optic lens in order to prevent pilots from being subjected to visual distortion. The precise optics for canopies and windshields are built into the injection mold. The injection molds are lapped or polished by hand, section by section, using a diamond plated lapping material. Hand polishing or lapping an injection mold takes several man-years to accomplish. Thus, lapping or polishing is very costly. Hand polishing or lapping also does not ensure that the precise, optic surface finish quality has been met.

[0005] Therefore, there exists an unmet need to reduce the cost and increase the accuracy of lapping or polishing.

SUMMARY OF THE INVENTION

[0006] The present invention provides end effectors for performing surface lapping using a robot. The end effectors allow orthogonal surface contact in order to maintain optimum pressure applied by the robot.

[0007] The end effectors include a base, a plate having a planar surface, a lapping pad that attaches to the planar surface of the plate, and a pivot joint. The pivot joint allows the plate to pivot about two axes. The base is attached to an arm of the robot.

[0008] In accordance with an aspect of the invention, the two axes are substantially parallel to the planar surface.

[0009] In accordance with an another aspect of the invention, the pivot joint includes a universal joint, a gimbaled joint, a half-ball and socket joint, or a crossed-pin ball and socket joint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.

[0011]FIG. 1 is a perspective view of an end effector in operation;

[0012]FIG. 2 is an exploded view of exemplary materials layered on an end effector;

[0013]FIGS. 3A and B illustrate a universal joint end effector;

[0014]FIG. 4 illustrates a gimbaled-joint end effector;

[0015]FIGS. 5A and B illustrate a one-half ball and socket end effector;

[0016]FIGS. 6A and B illustrate a cross-pinned ball and socket end effector; and

[0017] FIGS. 7A-C illustrate a multi-end effector support.

DETAILED DESCRIPTION OF THE INVENTION

[0018]FIG. 1 shows an embodiment of an end effector 40 according to the present invention that is attached to a robot 42 for polishing and lapping a work product 44. A non-limiting example of the product 44 is a core or cavity injection mold for making polycarbonate aircraft canopies. The work product 44 suitably entails a high degree of polishing or lapping accuracy. For example, precise optical properties for injection molds must be attained in order to produce optically flawless or near-flawless polycarbonate molded canopies. In order to attain this desired level of accuracy, the end effector 40 pivots at an end of the robot 42, but does not rotate about an axis that is perpendicular to a planar surface of the end effector 40. In other words, the end effector 40 maintains a substantially orthogonal position relative to the work product 44.

[0019] A non-limiting example of the robot 42 includes a Fanuc, Inc. robot with soft float. Soft float allows the robot 42 to apply pressure to a surface without resulting in undesired shut-offs. Because the robot 42 applies continuous, consistent pressure that far exceeds the capabilities of a human operator, lapping and polishing evolutions take a fraction of the time taken by a human operator.

[0020] As shown in FIG. 2, the end effector 40 suitably includes a lapping plate 50 with applied layers of materials that aid in lapping the work product 44. In one embodiment, the layers of materials include one or more silicone or polysulphide adhesive layers 54 interleaved with one or more solid acrylic rings 56. A pitch substance 60, such as tree pitch produced by Universal Photonics, Inc., Adolf Miller, or Zophar Mills, Inc., is applied to the last acrylic ring 56. A polishing or abrasive material 62, such as a diamond-plated lapping material, is attached to the pitch 60. The robot 42 applies pressure to the work product 44 through the end effector 40 in order to for the pitch 60 to conform to the surface of the work product 44. The robot 42 moves the end effector 40 over a section of the surface of the work product 44 that entails the same curvature to which the pitch 60 conforms.

[0021]FIGS. 3A and B illustrate a non-limiting example end effector 100 that suitably attaches to the robot 42 (FIG. 1). The end effector 100 includes a universal joint 104 that couples a base mount 106 to a lapping plate 110. The base mount 106 suitably attaches to the robot 42 (FIG. 1). The universal joint 104 suitably includes a U-shaped receiver portion 114, a pin housing 116, and a U-shaped lapping plate portion 120. The U-shaped receiver portion 114 is part of or is securely attached to the base mount 106. The U-shaped lapping plate portion 120 is suitably part of or is alternatively securely attached to, the lapping plate 110.

[0022] A first pin 124 is mounted through the U-shaped receiver portion 114 and the pin housing 116. The pin housing 116 rotates about a longitudinal axis of the first pin 124. Second and third pins 130 and 132 are mounted through the U-shaped lapping plate portion 120 and into the pin housing 116 to allow the U-shaped lapping plate portion 120 to rotate about a longitudinal axis of the second and third pins 130 and 132. The second and third pins 130 and 132 are substantially axially orthogonal to the first pin 124. Thus, the universal joint 104 allows the lapping plate 110 to rotate about the axis of the first pin 124 and the axis of the second and third pins 130 and 132 without allowing rotation of the lapping plate 110 itself.

[0023]FIG. 4 illustrates a gimbaled-joint end effector 150. The gimbaled-joint end effector 150 includes a base 154, a swivel ring 156, and a lapping plate 160. The base 154 is securely attached to the robot 42 (FIG. 1). The swivel ring 156 is suitably ring-shaped and securely receives first and second pins 164 and 166 on opposing sides. The pins 164 and 166 protrude outward from the swivel ring 156. The base 154 includes a circular cavity for receiving the swivel ring 156. The first and second pins 164 and 166 are rotatably received by walls that define the cavity of the base 154, thereby allowing the swivel ring 156 to rotate about a longitudinal axis of the first and second pins 164 and 166. The swivel ring 156 also receives a third pin 170 with a longitudinal axis that is orthogonal to the longitudinal axis of the first and second pins 164 and 166. The lapping plate 160 includes a circular extension 172 that is sized to fit within the swivel ring 156. The circular extension 172 rotatably receives the third pin 170. The lapping plate 160 rotates about the longitudinal axis of the third pin 170 within the swivel ring 156. The gimbaled-joint end effector 150 allows the lapping plate 160 to rotate about the longitudinal axis of the first, second, and third pins 164, 166, and 170 without causing rotation of the lapping plate 160 itself.

[0024]FIGS. 5A and B illustrate a one-half ball socket end effector 190. The one-half ball and socket end effector 190 includes a socket housing 194, a half-ball lapping plate 196, and first and second pins 200 and 204. The lapping plate 196 includes a one-half ball joint portion 206 that is pivotally received by a semi-circular cavity 208 formed by the housing 194. The pins 200 and 204 pass through opposite sides of the housing 194 and protrude into the cavity 208. The distance between the pins 200 and 204 is suitably less than a diameter of a widest part of the one-half ball joint portion 206. Thus, the one-half ball joint portion 206 swivels within the housing 194 and is maintained within the cavity 208 by the pins 200 and 204.

[0025]FIGS. 6A and B illustrate a cross-pinned ball and socket end effector 230. The cross-pinned ball and socket end effector 230 includes a base 234, a lapping plate 238, a ball pin 242, and securing pins 250 and 252. The base 234 includes a ball assembly 240 that is substantially spherical and that receives the ball pin 242 through approximately the center of the ball assembly 240. The ball pin 242 is suitably longer than the diameter of the ball assembly 240. The lapping plate 238 includes a ball cavity 244 that rotatably receives the ball assembly 240. The lapping plate 238 also includes pin cavities 246 that are located adjacent to the ball cavity 244 on opposite sides of the ball cavity 244. The ball pin 242 is inserted into the ball assembly 240. The ball assembly 240 with ball pin 242 are inserted into the ball cavity 244 with the ball pin 242 being received by the pin cavities 246. The securing pins 250 and 252 mount through the lapping plate 238 and the pin cavities 246, respectively. The securing pins 250 and 252 keep the ball pin 242 within the respective ball pin cavities 246. The lapping plate 238 pivots about a longitudinal axis of the ball pin 242. The lapping plate 238 also rotates about an axis substantially orthogonal to the longitudinal axis of the ball pin 242. This is because the ball pin cavities 246 are sized to allow pitching motion of the ball pin 242 therein.

[0026] FIGS. 7A-C illustrate a multiple end effector support 350. The multiple end effector support 350 includes a plurality of arms 356 that extend radially from a center shaft 360. The center shaft 360 is attached to a base (not shown) that is coupled to the robot 42 (FIG. 1). As shown in FIG. 7C, an extension 364 extends from a single end effector unit 366. The type of end effector unit that can be used is any one of the ones shown in FIGS. 3-7. The multiple end effector support 350 suitably includes two or more arms 356 for polishing and lapping a large area. In another embodiment, small and large lapping plates are alternately connected around the multiple end effector support 350.

[0027] In one embodiment, the extension 364 is suitably a threaded shaft that is received by a threaded cavity near an end of an arm 356. The extension 364 is secured to one of the arms 356 by a securing pin 370 that tightens a split at the end of the arm 356. The split extends to the threaded cavity.

[0028] While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow. 

What is claimed is:
 1. A robotic system for lapping a surface, the robotic system comprising: a robotic arm; and an end effector unit including: a base attached to the robotic arm; a plate having a planar surface; a lapping pad attachable to the planar surface of the plate; and a pivot-joint for allowing the plate to pivot about two axes.
 2. The system of claim 1, further comprising a pitch for attaching the lapping pad to the lapping plate.
 3. The system of claim 1, wherein the two axes are substantially parallel to the planar surface.
 4. The system of claim 3, wherein the pivot-joint includes a universal joint.
 5. The system of claim 3, wherein the pivot-joint includes a gimbaled joint.
 6. The system of claim 3, wherein the pivot-joint includes a ball and socket joint.
 7. The system of claim 6, wherein the ball and socket joint includes a half-ball and socket joint.
 8. The system of claim 6, wherein the ball and socket joint includes a crossed-pin ball and socket joint.
 9. The system of claim 1, wherein the lapping pad includes a diamond lapping pad.
 10. A lapping end effector comprising: a base; a plate having a planar surface; a lapping pad attachable to the planar surface of the plate; and a pivot-joint for allowing the plate to pivot about two axes.
 11. The system of claim 10, further comprising a pitch for attaching the lapping pad to the lapping plate.
 12. The system of claim 10, wherein the two axes are substantially parallel to the planar surface.
 13. The system of claim 12, wherein the two axes are substantially orthogonal to a direction of pressure applied to the plate.
 14. The system of claim 12, wherein the pivot-joint includes a universal joint.
 15. The system of claim 12, wherein the pivot-joint includes a gimbaled joint.
 16. The system of claim 12, wherein the pivot-joint includes a ball and socket joint.
 17. The system of claim 16, wherein the ball and socket joint includes a half-ball and socket joint.
 18. The system of claim 16, wherein the ball and socket joint includes a crossed-pin ball and socket joint.
 19. The system of claim 10, wherein the lapping pad includes a diamond lapping pad.
 20. A robotic system for lapping a surface, the robotic system comprising: a robotic arm; a support member coupled to the robotic arm; and a plurality of end effector units including: a base attached to the support member; a plate having a planar surface; a lapping pad attachable to the planar surface of the plate; and a pivot-joint for allowing the plate to pivot about two axes.
 21. The system of claim 20, wherein the two axes are substantially parallel to the planar surface.
 23. The system of claim 21, wherein the two axes are substantially orthogonal to a direction of pressure applied by the robotic arm.
 24. The system of claim 21, wherein the pivot-joint includes a universal joint.
 25. The system of claim 21, wherein the pivot-joint includes a gimbaled joint.
 26. The system of claim 21, wherein the pivot-joint includes a ball and socket joint.
 27. The system of claim 26, wherein the ball and socket joint includes a half-ball and socket joint. 28 The system of claim 26, wherein the ball and socket joint includes a crossed-pin ball and socket joint.
 29. The system of claim 20, wherein the lapping pad includes a diamond lapping pad.
 30. A method for lapping a surface, the method comprising: applying pressure by a robot between a lapping pad attached to a plate having a planar surface and the surface; and pivoting the plate to move about two axes, wherein the two axes are substantially parallel to the planar surface and the applied pressure is substantially orthogonal to the two axes. 